Electric clock system



Oct. 10, 1944. o. H. DICKE I ELECTRIC CLOCK SYSTEM Filed Nov. 8, 1958 4Sheets-Sheet l 0605f l n r 583 m: E #m j L E588 1L 2m m 3 26?; En: 098 m-m 2 28283 $.88 v EEEQH ooaefioonmn x wm+d5u u I .11. T so 3 .H L

.ii.lDlCfl(E ELECTRIC CLOCK SYSTEM Oct. 10, 1944.

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Patented Oct. 10, 1944 UNITED STATES PATENT OFFICE ELECTRIC CLOCK SYSTEMOscar H. Dicke, Rochester, N. Y.

Application November 8, 1938, Serial No. 239,538

21 Claims.

The present invention relates to time control systems and moreparticularly to time clock systerns driven by synchronous motors forpunching or printing on a time card the time of arrival and departure ofan employee to and from his place of employment, indicating time inrailway stations, schools and oflice buildings, and the like.

In systems of the above typ the secondary clocks may be corrected in thefifty-ninth minute, in that extreme accuracy in the last minute is notimportant.

In accordance with the present invention a slow secondary clock isadvanced by a second or auxiliary synchronous motor which has a higherspeed or is connected to the time shaft by a gear train having a highergear ratio so as to rotate the time shaft at a higher speed; or iscorrected by the same motor by operating it from higher frequencyalternating current during the correcting period so as to make the timeshaft run faster during correction of a slow clock. In accordance withthe present invention a fast clock is corrected by stopping thesecondary clock at a certain time indicating point and to again allow itto advance when the master clock reaches a corresponding time indicatingpoint or several points.

One of the objects of the present invention resides in th employment ofone or more synchronous alternating current motors in each secondaryclock and to correct such secondary clock without the use of costlyrelays, electro-magnetic setting means or the like, synchronous motorsbeing less costly to build than relays.

Another object f the present invention is to render the secondary clocksvery quiet not only during the clock advancing period but also duringthe clock correcting period.

Another object of the present invention resides in the provision ofnovel master clocks in which one element of the master clock used foroperating clock correcting contacts is always in substantial synchronismwith the secondary clocks in spite of the fact that the secondary clocksare at rest during alternating current cessation, such current beingderived from a commercial power system having its frequency regulated tocorrectly manifest passing of time.

Other objects of the present invention reside in the provision of masterclocks in which joint action of escapement mechanisms and synchronousmotors driven by alternating current of regulated frequency correctlymanifest th passing of time and in which the master clock time shaft isadvanced in accordance with current cycle passage during the presence ofalternating current.

Other objects, purposes and characteristics and their advantages willappear from the following description when taken in connection with thedrawings and from the drawings themselves in which:

Fig. 1 shows a three wire clock system in which the secondary clocksemploy a double rotor double stator synchronous motor and in which themaster clock comprises an alternating current dominated escapementclock;

Fig. 2 is a modified form of the invention in which an alternatingcurrent master clock is employed which master clock after each powerfailure is corrected by a normally stationary escapement clock and inwhich a single rotor secondary clock is automatically kept correct withthe master clock over a single circuit through the medium of currents ofdifferent frequencies;

Fig. 3 is a modification which includes a master clock similar to Fig. land employs currents of two different frequencies like in Fig. 2 butemploys two circuits, one being used for normal advancing of thesecondary clocks and for making a rough correction after each currentcessation and the other being used for making a refined correctionperiodically;

Fig. 4 illustrates an enlargement of main spring gear, its extra long,engaging pinion and the manner in which the main spring gear takes alateral position on its shaft in accordance with the extent of Windingof the main spring.

Fig. 5 illustrates how a continuously running minute shaft mayintermittently drive an hour shaft so as to present a new type numberevery minut during the normal operation of the secondary clock.

Fig. 6 shows how Fig. 1 may be modified to eliminate one line wire.

Fig. '7 shows how the master clock of Fig. 2 may control the secondaryclock of Fig. 1 by elimination of a second frequency current and by theaddition of an extra line wire.

8 shows how the secondary clocks of Fig. 1 may be controlled by a masterclock including an auxiliary source of alternating current; and

Fig. 9 shows the clock dial of a further modification.

The inventions disclosed in this application are improvements over theinventions disclosed in my prior applications Ser. No. 365,584 filed May23, 1929, now Patent No. 2,2 gr d y 8, 1941; Ser. No. 441,109 filedApril 2, 1930, now

Patent No. 2,331,267 granted Oct. 5, 1943; Ser. Nos, 729,079 and 729,080filed June 5, 1934, now respectively patents, Nos. 2,248,165 and2,185,334 granted respectively on July 8, 1941, and January 2, 1940; andthe application of Robert H. Dicke Ser. No. 39,146 filed September 4,1935, now Patent No. 2,151,317 granted March 21, 1939.

In accordance with the present invention it is proposed to employ orhave available a commercial alternating current power distributing system delivering current of regulated frequency, that is, current havingits average frequency regulated to correctly manifest time by cyclepassage or summation. In each case the master clock is of a constructionto be dominated so as to run in synchronism with alternating currentcycle passage (see Figs. 1 and 3) or a construction including anelectric master clock which is corrected in accordance with the durationof a current cessation after such current cessation (Figs. 2 and 7). Thesecondary clocks which they control may be used as tower clocks, as hellringers or for any other program purpose.

It is also proposed to have secondary clocks of extremely simpleconstruction. It is found that it is more economical to add an auxiliarymotor than to add a relay, or an electrically operated clutch or gearshift. This is especially true if the added synchronous motor has itsrotor mounted on the same shaft with the main motor so that noadditional bearings are required as is the case in applicantsconstruction in Figs. 1, 6 and '7. It is also proposed to employcontacts to temporarily stop the secondary clock by opening the motorcircuit to correct a fast sec ondary clock. In order to correct a slowclock it is proposed to employ a higher frequency alternating current,possibly a current of double frequency, see Figs. 2. and 3 for instance,or to apply current of the same frequency to a higher speed motor, suchas a stator acting on a fewer poles rotor, see Figs. 1, 6 and '7, forinstance. In each of Figs. 1, 2, 3, 6 and '7 the secondary clock isadvanced after each alternating current cessation and is speciallycorrected at the end of each particular time interval such as an hour,and if the first mentioned correction carries through such even hourpoint on the secondary clock a special release is given to suchsecondary clock so that the feature which normally stops the clock whenit has reached the even hour position cannot be effective. In the formof the invention shown in Fig. 3 similar corrections are made but thecorrection made after each power or current cessation is made through acircuit which does not include a contact broken by the secondary clockso that no such special release is necessary.

In the construction of Figs, 1, 6 and '7 the secondary clock is one inwhich two synchronous motors having common bearings is employed. Asillustrated, one of these motors has a six pole rotor and has asynchronous speed of 1200 R. P. M. whereas the other has a two polerotor and has a synchronous speed of 3600 R. P. M., and the constructionis such that normally only the 1200 R. P. M. motor is energized.

Fig. 1 structura-In this form of the invention an escapement masterclock including the usual escape wheel I and pendulum 2 is employed. Theescape wheel I is driven by the main spring 3 through the medium ofgears 4 and 5 and pinions 6 and 1. This main spring is normally rewoundat exactly the same rate that it runs down,

the two worm reductions 89 and |0H being such that with synchronousmotor 5M running at 1200 R. P. M. the shaft 12 is rotated at exactly 1R. P. H. On this shaft is mounted an insulating block I4 having contacts15 and I5 mounted thereon. These contacts are biased toward each otherand if free are in actual contact with each other. When the main spring3 is fully wound the contact l5 engages the pin ll of insulatingmaterial, thus separating contacts l5l6 and opening the circuit for therelay R unless the circuit for this rela R was already open at contacts202l. Either of the synchronous motors SM and SM may also drive therotary circuit closer 23 as through the medium of pinion 24 and gear 25.The pendulum 2 is dominated in any suitable manner as byelectro-magnetic impulses as through the medium of electro-magnet 2!28.This electro-magnet 2728 has the poles of the magnetic core 21 providedwith rubber bumpers 29, for the purpose of silencing the impacting ofthis electro-magnet 2l28 by the pendulum. This dominating of a pendulumby electro-magnetic impulses is also disclosed in my prior applicationSer. No. 365,584 above referred to. It should be noted that the circuitfor electro-magnet 2l28 is closed at a rate three times as fast when therotary circuit closure is driven by motor 8M than when driven by motorSM this however does not detract from effective domination of thependulum by the electro-magnetic impulses, because two of the threeimpulses occur when the pendulum is far away from the electromagnet andfurthermore because the effect of these two impulses is neutralizedbecause one occurs when the pendulum is approaching and the other whenthe pendulum is receding. It may be pointed out that the pendulum isdominate-d in the following manner. When the pendulum is a little slowthe electro-magnetic impulses accelerate it by first causing an increasein amplitude of the pendulum and by then aliowing the pendulum to bounceoff of the electro-magnet, so to speak. If the pendulum is fast it isheld in contact with the electro-magnet temporarily at the end of eachmagnetic impulse, or is at leastretarded when receding. It is this factof domination of theescapement clock by a regulated frequencyalternating current which current also drives the synchronous motor SMthat keeps the gear 4 and the shaft I2 in absolute synchronism andthereby keeps the contacts l5-l6 just barely open, when they have oncebeen opened, so long as no current cessation occurs. The winding shaft12 has mounted thereon two contact operating disks K and K These diskshave been mounted to rotate with shaft I2 rather than with gear 4 sothat these disks remain at rest during a power cessation and rotate at ahigher speed when high speed winding, through the medium of synchronousmotor SM takes place. Each secondary clock, only two of a pluralityhaving been shown, comprises an hour shaft 3| driven at 1 R. P. H. bythe synchronous motor 8M and driven at 3 R. P. H. by the synchronousmotor 8M through the medium of a gear reduction train shownconventionally by the gear 32 and the pinion 33. This shaft is similarlyprovided with contact operating disks K and K which operate contacts42-43 and 38-49 respectively.

Operation Fig. 1.Duri'ng normal operation of the clock system thependulum 2 is in engagement with the energized electro-magnet 2728during each right hand stroke of the pendulum, the electro-magnet beingenergized intermittently once fo each period of the pendulum when thispendulum is adjusted to keep correct time. That is, if the pendulummakes a complete cycle in one second the contact 23 energizing theelectro-magnet 21-28 closes once for each second when driven by thesynchronous motor SM and once each one-third second when driven by thesynchronous motor M If the pendulum is a little slow it is acceleratedby the electro-magnet and if a little fast it is retarded thereby. Alsoduring normal operation of the system the secondary clock is operatedbetween the zero minute and the fifty-nine minute position, as reflectedby the clock hand 34 of the master clock, by the synchronous motor 5Mthrough the following circuit: beginning at the source of alternatingcurrent comprising the secondary winding of transformer T which has itsprimary winding fed from the commercial alternating current power systemAC of regulated frequency, back contact 35 of relay R normally closedcontacts 36-31 operated by the disk K low speed wire L contacts 38-39,operated by cam or disk K wire 45, winding of the synchronous motor 5Mto the common return wire C which is connected to the other terminal ofsaid secondary winding. During the period between the fifty-nine minuteand sixty minute position of the master clock alternating currentvoltage is applied to the following circuit: beginning at one terminalof the secondar winding of transformer T back contact of relay Rcontacts 36-4I operated by cam K high speed wire H contacts 42-43, wire46, and high speed motor SM, of the secondary clock S through commonreturn wire C back to the other terminal of the secondary winding oftransformer T If the secondary clock was correct at the beginning of thefifty-ninth minute of the master clock it will be operated by current inthe last traced circuit for twenty seconds at which time the secondaryclock S reaches the even hour position as reflected by the clock hand44, contacts 42-43 open. This is true because the secondary clock S willrun at three times normal speed during these twenty seconds. If thesecondary clock was slow from zero to two minutes it will runcorrespondirigly longer. For instance, if it was slow fifteen seconds itwill run five seconds longer. It will be noted that contacts 38-39 areopen between fifty-nine minutes fifty seconds position and thefifty-nine minute fifty-nine seconds position. From which it is apparentthat contacts 38-39 will be reclosed by operation of synchronous motor8M through the last traced circuit unless the secondary clock was slowmore than two minutes. The secondary clock will however not be slow formore than two minutes because it is corrected to an extent depending onthe duration of a power failure or current cessation immediately aftersuch current cessation terminates.

For instance, let us assume that the secondary clock S is exactlycorrect with the master clock MC and that a fifteen minute currentcessation starts at the fifteen minute position of the shaft I2 andclock hand 34 of the master clock MC and the fifteen minute position ofthe shaft SI and clock hand 44 of the secondary clock S These shafts I2and 3| will immediately stop, because these shafts were driven bysynchronous motors SM and 8M respectively. During the fifteen minuteperiod of current cessation the pendulum 2 will not be dominated by the.electro-magnet 21-2 8, because there is no source seven and one-halfminute position.

of current AC present, and this is true even though contacts 23 happento be closed during the time of current cessation. The pendulum willhowever very closely measure the duration of current cessation. Afterfifteen minutes, that is, when the gear 4 of the master clock M0 assumesthe thirty minute position, as above assumed, alternating current isagain available. Since however gear 4 has continued to operate, due tothe main spring 3 driving the escape wheel I, the contacts I5-I6 are nowclosed and the relay R picks up immediately upon the return ofalternating current. When this happens the contact 46 of relay Rdisconnects the winding motor SM operating at 1200 R. P. M., and insteadconnects the winding motor SM operating at 3600 R. P. M. It is thusobserved that the shaft I2 operates three times as fast as the gear 4for which reason the contacts I5-I6 would reopen fifteen-thirds of theminutes later, that is, would open five min utes later if the escapementstood still. Since the escapement portion of the master clock continuesto operate the pin I'I continues to move away from the contact I5. Thatis, the contact I5 gains with respect to the pin H at the rate of tenseconds for each five seconds of operation and therefore the contactsIE-IB will remain open seven and one-half minutes after the return ofthe alternating current power or at the thirty-seven and one-half minuteposition of the master clock. During this seven and onehalf minuteperiod immediately after the fifteen minute current cessation the shaftI2 was operated from the fifteen minute position to the thirty- Thisoccurred because the synchronous motor M operates at three times. thespeed of synchronous motor SM During this seven and one-half minuteperiod the contact 35 of relay R assumed its raised position andtherefore operated the synchronous motor 5M of the secondary clocks,only two such clocks S having been shown, through the followingcircuitz-startin-g at one terminal of the secondary winding oftransformer T front contact 35 of relay R high speed wire H contacts42-43 of secondary clocks, each having a synchronous motor 8M connectedin series therewith, through the common return wire C and back to theother terminal of the secondary winding of transformer T During thisseven and one half minute interval the secondary clock will be operatedat triple speed and will therefore assume the thirty-seven and one-halfminute position when the current flow over the line wire H isterminated.It is possible that there might be u slight error in this correction dueto mechanica and electrical limitations, but this error will be removedat the end of the hour by the supplemental correcting function performedby the contacts 35-31-4I operated by the cam K of the master clock, andany error that may be made by this supplemental correcting means willnot be cumulative.

Let us now assume that the master clock MC I and the secondary clock Sassume the forty-five forty-five minute position the contacts. 2.0.-2landv 36Sl are closed and contacts 3.64| are open. Upon the resumption ofalternating current flow the relay R is energized, thereby closing theenergizing circuit for the synchronous winding motor SM which. windsthemain. spring at three times the speed of operation of gear 4. In otherwords, the winding motor is operating at a speed so that pin l1catchesup two-seconds for every second of operation and the contact [-45will open in ten minutes. Also with relay R energized the secondaryWinding of transformer T is connected directly across wires H and C sothat the motor 3M of. the secondary clock is energized through contactsc2 4'3. and the secondary clocks S operate at three times normal speed.These contacts 42'-43 will however open after five minutes of operationof the-synchronous motor SM because this motor SM operates at thre timesthe speed of synchronous motor M and the contacts 4243 open at exactlythe end ofthe hour as manifested by the secondary clock shaft and itsclock hand 44: The secondary clock and the cams K and K of the masterclock assume substantiallythe same position since both have beenoperated at three times normal speed from the forty-five minute positionsince alternating current power returned. In other words, at the timethat the contacts 4243 of the secondary clock S opened the contacts2B2'l and 36-4! of the master clock MC opened and'contacts 363? of themaster clock M0 closed. Opening of contacts 2!l2l for tensecondsdeenergizes the relay R for ten seconds, so that curernt may forten seconds flow from the secondary winding of transformer T throughback contact 35 of relay R through contacts 363 'l, through wire Lthrough contacts 38-39 of the secondary clock, which closed just beforecontacts 632-t3 opened, through synchronous motor M through commonreturn wire C back to the secondary winding of transformer T Thesecondary clock will therefore run at normal speed for ten seconds, aswill also the cams K1 and K of the master clock. because with relay RdeenergL-Zed these cams will be driven atnormal speed by the synchronouswinding motor 8M At the end of this ten second period the cam K of thesecondary clock S will reclose its contacts 22-43 as will also the cam Kof master clock M0 reclose contacts 2ii-2l thereby reenergizing therelay R 'Ihiswill re-establish the high speedcircuit through frontcontact 35 of relay R1 and contacts 42 and 43 of secondary clock S Whenthe-masterclock now assumes the fifteen minute ten second position (:10)the winding contacts |5-l6 will open, thereby deenergizing the relay Rand dropping'its contacts and 46; Dropping of contact d6 will substitutethe synchronous winding'motor 8M for synchronous winding motor 8Mthereby causing winding of the master clock at the same rate as its mainspring runs down, thependulum of the master clock being dominated by thealternating current impulses applied by the contacts 23. Dropping ofcontact 35,- with contacts 38-37 closed, causes the normal or low speedcircuit for the secondary clock and including contacts 38-39and lowspeed synchronous motor M to be closed, so that the secondary clockagain operates at normal speed.

By reason of the shifting from one motor to another at both the masterclock M0 and the secondary clocks there may be aslight error in thesecondary clock, but this error should not exceed a few seconds and thiserror will be removed at the end of the hour by the refined correctingmeans including contacts 36, 3'! and M of the master clock, theoperation of which has been explained above. All of the contactsmentioned will of course be designed to give a little leeway to takecare of inaccuracies in time.

Putting it briefly, the clock system shown in Fig. 1 is of aconstruction such that if a current cessation occurs which is of aduration so that it may be corrected through a circuit including frontcontact 35 of the relay R before the end of the hour as manifested bythe master clock, a correction of all secondary clocks will be made byoperating all of these secondary clocks at three times normal speed fora time equal to half of the period of current cessation. If, however,the outage is such that this correction carries it through the even hourposition then the secondary clocks are all temporarily operated throughthe low speed circuit and contacts 3839 at normal speed for a ten secondinterval, this in order that the contacts 4243 of all the secondaryclocks may be reclosed, after which the correction by operating allsecondary clocks at three times normal speed again continues until theyhav been corrected to within a few seconds. This ten second interval isdetermined by contacts Zil-Zl which deenergize and drop the relay R forten seconds. This correction may be in error to an extent of severalseconds and because this error for successive corrections would becumulative the applicant has provided a refined or supplementalcorrecting means which corrects in accordance with contacts controlledby the position assumed by the time shaft of the master clock, andtherefore such error as there may be is not cumulative. Thissupplemental correcting means constitutes apparatus and contactsassociated with the master clock for applying with the relay Rdeenergized current to the high speed circuit H during the last minuteof the hour and which is capable of holding a secondary clock back, ifit is fast, to an extent of 59 seconds and can advance a slow clockto-the extent of one minute and fifty-nine seconds.

In the above description the time ofopening and closing of. the variouscam operated contacts has been very precisely set forth. It should,

, however, be understood that the applicant does not limit himself tothese precise values, these values having been, to a certain extent,chosen to facilitate description of the invention. Also, since thesecondary clock during a correction following a power failure, that is acorrection made by the relay R the secondary clock S may not b correctwith respect to shaft I2 of the master clock MC a certain allowanceshould be made. If under this condition the secondary clock isconsiderably slow the contacts 42--43 might not. have reclosed duringthe deenergh zation of relay R Therefore, if desired, the contacts 202Iof the master clock may be constructed to open later and be open muchlonger, say for one-half minute or even longer. This would allow greatermargin to take care of'inaccuracies. In fact in one construction thecontacts 2fi.2l may be open between the tenth'and the thirtieth secondof the hour. This would take care of any secondary'clock that is fromten seconds slow to ten seconds fast with respect to the shaft l2.Similarly the other contacts may be varied in degree to allow'marginsfor mechanical inaccuracies. The indicating lamp IL indicates when theclock is being advanced.

Fig. 2 structure.In the structure of Fig. 2 the functional results aresubstantially the same as those accomplished by the structure of Fig. 1.The structure, however, employs only two line wires and the master clockMC is a synchronous motor operated clock with escapement clock governingmeans for causing the synchronous motor clock to run at double speedafter each current cessation for a time equal to the time of suchcurrent cessation, as is also true of all secondary clocks, only twohaving for convenience been illustrated, the double speed being obtainedby applying a double frequency. One of these secondary clocks has beenshown structurally and the other has been shown conventionally but bothhave been designated S Referring to Fig. 2, the master clock MC includesa synchronous motor SM which when operated by normal frequency ofpreferably 60 cycles will drive the hour shaft 50 at 1 R. P. H. througha gear reduction including pinion 5| and gear 52. This shaft 50 drivescontact operating cams K and X operating and controlling contacts 545556and 5'|'5859 respectively. This synchronous motor CM is, during thpresence of alternating current of regulated frequency derived fromthesource AC, supplied with either normal frequency alternating currentthrough transformer T or is operated by alternating current of doublefrequency derived from transformer T as determined by the condition ofenergization of relay B? through its contact 60. The transformer T issupplied with pulsating current of 120 cycle frequency through themedium of a frequency doubler, comprising thyratrons TR and TR Thesethyratrons are really gas filled grid initiated or grid controlledrectifiers, each having a grid g, a filament f and a plate 22. The gridsare each provided with a grid leak r and are activated from thesecondary winding 63 of the transformers T The filaments f are alsoenergized from a secondary winding (not shown) of this same transformer.The various constants are preferably so chosen that rectification ofsubstantially the second half of each half, namely, the second half ofthe positive and th second half of the negative wave of each cycle ofcurrent is rectified. This is done in order that the rectified waves,derived from the plate circuits including secondary winding 64 oftransformer T and which currents flow in the same direction in theprimary winding of the transformer T may be separated by a time periodsubstantially equal to their duration, so that alternating current of120 cycle and of substantial quantity will be delivered at the terminalsof the secondary winding of thi transformer T In order to get therectifying action for each wave of the alternating current to be startedby its thyratrcn at or near the middle of the current wave it may benecessary to employ suitable phase shifting apparatus. Such phaseshifting apparatus is employed for properly phasing the grid circuit fortube TB in the prior application of Hoppe Ser. No. 120,421 filed January13, 1937, now Patent No. 2,131,735, dated October 4, 1938, to whichreference may be had. This phase shifting apparatus comprises aninductance PL and a resistance PR of the prior application connected inseries across the secondary winding of a transformer, with the potentialdifference between an intermediate point of said secondary winding andthe junction between said inductance PL and said resistance PR. as thephase displaced electro-motive force to activate the grid of thethyratron.

This master clock MC includes an escapement clock mechanism and asynchronous motor clock mechanism in combination. This escapement clockis shown conventionally as a pendulum clock, comprising a pendulum 55,having a soft iron magnetic bob 65 normally held at rest by the directcurrent electro-magnet Eli-Bl energized by direct current derived fromthe same source of regulated frequency current through the medium ofrectifier R1 This electro-magnet has each leg surrounded by a ring orslug of copper or other suitable conducting material in order to makethe direct current magnet slow releasing. This electro-rnagne-t is madeslow releasing in order that the escapement clock may measure a slightlysmaller time than the actual time of a current cessation and in so doingwill cause the relay R to be energized a correspondingly shorter time inorder that the synchronous motor SM will be energized by doublefrequency alternating current a slightly shorter period than the actualduration of the current cessation. This is done to remove the error thatwould otherwise creep in due to the coasting of the motor 3M during thecurrent cessation. It has been found that if a small synchronous motorof the type contemplated is energized for one second it will rotate anextent equal to one and one-half seconds. That is, if it is two pole itWill rotate 90 revolutions instead of 60. This pendulum controls anescape wheel iii which is driven by a main spring 1! through the mediumof gears 12 and i3 and p-inions l4 and 15.

This main spring ll is electrically Wound through the medium of shaftll, worm-wheels l8 and 19 and worms and 8| by the synchronous windinmotor 5M This worm reduction gearing including worm-wheels 18 and I9 andworms 80 and BI has a rotation ratio such that when the spring windingmotor SM operates at synchronous speed from the alternating currentregulated source it will turn the shaft ll exactly one revolution in onehour. In other words, if a current cessation has occurred, upon returnof power the contacts 84-85, which are normally held open by the pin 85being engaged by the contact 84 and holding it away from the contact 85,and which are closed by any power cessation of less than one hour, willbe opened when the power has been restored for a time equal to theextent of the duration of such cessation minus about a half second. Thishalf second difference is due to the fact that the escapement ran a halfsecond less time than the extent of the power cessation, and this was byreason of the slow acting release of the brake magnet due to its slug63. The rectifier R1 is also included in series in the energizingcircuit for the relay R to render the relay quiet.

Referring now to the secondary clock, each secondary clock, only twohaving been shown both designated S includes a minute shaft 929(rotating one revolution per hour) driven by a synchronous motor 5Mthrough reduction gearing including pinion 9| and gear 22. The S9 drivestwo cams K and K which control snap acting contacts S6 and 9'l98,respectively. The contacts El i8 snap open at 59:50 (meaning fifty-nineminutes and fifty seconds) and snap closed at 59:59, Whereas thecontacts 95-416 snap open at the end of thesixtleth minute and snapclosed at the end of the tenth second of the hour. The contacts 95-96have included in series therewith two tuned units C I and C I Thecondenser C and'in ductance I are included in series and tuned tocurrent resonance at 120 cycles and the condenser C and inductance I areconnected in multiple to resonate at 60 cycle potential to greatlyrestrict the flow of 60 cycle current, thus allowing the free flow ofcurrent of 120 cycles. Similarly, condenser C and inductance I areincluded in series to resonate for current res onance at 60 cycle atpermit the free flow of 60 cycle and restrict the flow of 120 cyclecurrent,

whereas the condenser C and inductance I are connected in multiple andhave values of capacity and inductance to cause them to resonate at 120cycle potential resonanceto greatly restrict the flow of 120 cyclecurrent while not materially restricting the flow of 60 cyclealternating current.

Operation Fig. 2.Under normal operating conditions 60 cycle or lowfrequency current is applied to the line wire L between the zeroposition and the 59:00 minute position of the master clock as indicatedby clock hand 99 through the fOlIOWlllg circuit: starting at secondaryof transformer T back contact Hll of relay R contacts 5l58 controlled bycam K wire L condenser C inductance I condenser C and inductance I inmultiple, contacts 91-93 operated by cam K synchronous motor SM commonreturn wire C back to the secondary winding of transformer T Under thisnormal condition the secondary clock S operates at normal speed and theescapement portion of the master clock is of course at rest, there beingnormally no power failure. During the entire sixtieth minute of themaster clock (see hand 99), when the contacts '51, 58 and 59 are intheir actuated position as shown in the drawings the contacts 5359 areclosed and th contacts 5158 are open. Under this condition current ofhigh frequency, namely, 120 cycle, in the particular system illustrated,is applied to the synchronous motors of the secondary clocks, only onemotor having been shown, through the line circuit including back contactI02 of relay R contacts 5958, line wire L condenser C and inductance Iin series and coni denser C and inductance I in multiple, and includingthe contacts 95-95 controlled by the cam K The synchronous motor SMwill, of course, operate at double normal speed when energized bycurrent of doubl frequency. At

the 59:30 minute position of the master clock the contacts 9596 of thesecondary clock will open, namely, when the secondary clock assumes the60:00 minute position (see hand 93) it having operated at double speedduring this time. The secondary clock will then stop, and at the 60:00minute position as manifested by the clock hand 99 of the master clockthe contact 58 of the master clock will shift from the contact 59 to thecontact '51, thereby reapplying current of 60 cycle frequency to thesecondary clock. It is desired to point out that 60 cycle current canonly reach contacts 9'l98 and likewise current of 120 cycle frequencycan only reach contacts 9596 of the secondary clock. This is the casebecause unit C -I is tuned to 120 cycle and permits the free flow of 120cycle current but restricts the flow of 60 cycle current, Whereascondenser C and inductance I are tuned to 60 cycle so as to restrict theflow of 60 cycle current but they allow comparative free flow of 120cycle current. On the other hand, unit C I is tuned to 60 cycle and unitI C is tuned to 120 cycle for similar purposes, that is, to allow thefree flow of 60 cycle current but to restrict the flow of 120 cyclecurrent.

' Let us now assume that at the 30 minute position of the master clockMC and the secondary clock 8 a current cessation takes place. Thiscessation of current deenergizes the brake magnet 66--6l causing it torelease the pendulum after about one half second delay. Since thesynchronous motor 8M will coast for an equal period of time theescapement clock will still measure the amount of time the electricsynchronous motor part of the master clock will have lost upon return ofthe alternating current power. This operation of the escapement portionof the master clock causes the main spring H to run partly down, causingthe pin 86 to dis- ,engage from the contact spring 84 thereby causingthe contacts 8485 to close. The relay R remains deenergized until powerreturns which we will assume to be at the forty minute position of themaster clock. This return of power will cause locking of the pendulum 65against the brake magnet 6661 and will cause picking up of the relay RPicking up of the contact 60 of the relay R will cause the synchronousmotor part of the master clock MC to run at double speed, because thesynchronous motor SM is energized by double frequency current. Alsolifting of the contact I02 of relay R applies current through the frontcontact I02, the closed contact -55, line wire L the tuned unit C I theuntuned unit C I for 120 cycle current, the contacts 85-435 through thewinding of synchronous motor SM", back to the 120 cycle source. Thiswill of course cause the secondary clock S to advance at double speed.Both of the shafts 50 and '90 will therefore run at double speed andthis will continue for a time equal to the duration of the currentcessation. This is true for at the -expirati0n of such a period of timethe contacts 84-85 of the master clock will be opened, resulting indeenergization of the relay R stopping of the winding motor SM and thereturn to normal speed of the synchronous motors 8M and SM". The shaft50 will therefore reflect exactly correct time and the shaft willreflect substantially correct time.

As the shafts 50 and Si! continue to run in substantially synchronousrotation the contacts i-5'8 open and the contacts 5359 close, thisoccurring near the end of the hour of the secondary clock and at thebeginning of the sixtieth minute of the master clock MC This will cause1 0 cycle frequency instead of 60 cycle frequency current to be appliedto the secondary clock This 120 cycle current can however, by reason ofthe tuned units, flow only through contacts GEL-96, and these contacts96 open at exactly the end of the hour as reflected by the hand 93 ofthe secondary clock. If the secondary clock was as much as 59 secondsfast it will be held at the end-of-hour position and if it was as muchas a minute slow it will reach the end-of-hour position by the time themaster clock reaches the end-of-hour position. The secondary clock willthus receive a refined correction, which cannot have a cumulative error,and this takes place at the end of each hour.

Let us now assume that a power cessation occurs that either continuesthrough the end-of- 75 hour position or in which the correction carriesthrough the end-of-hour position of the master clock. Let us assume thata power cessation of 20 minutes starts at the 50 minute position of themaster clock.

As heretofore pointed out all the electrical apparatus stops during acurrent cessation and the escapement portion of the master clock MCoperates during such current cessation. At the end of the twenty minutecessation the pin 86 will have moved away from the spring contact 84 anarc of substantially one-third of a revolution.

Upon return of power the pendulum 65 is braked, the winding synchronousmotor SM is started and the synchronous motors SM and SM are started andrun at double speed. Since shafts 50 and 90 are both driven at twicenormal speed the contacts 51-58 open after power has been on again forfour and one-half minutes, that is, when shaft 50 assumes the 59 minuteposition, but since high frequency current (120 cycles) flows directlyto the line wire L from the front contact I02 through contacts 54-55,the opening of contacts 57-58 is of no importance particularly sinceback contact I! is open. Also, the closing of contacts 58-59 is of noimportance since back contact I02 of the relay R is open. At the 59:50minute position of the secondary clock S and the shaft 90 the contacts91-98 open but this is of no immediate importance since no current hasbeen flowing therethrough. These contacts 97-98 reclose at the 59:59minute position of shaft 90. At the 60:00 minute position of the masterclock and the secondary clocks and shafts 50 and 90 the contacts 54-55open and contacts 55-56 close (see master clock) and the contacts 95-96of the secondary clock S open. The opening of either contacts 54-55 orcontacts 95-96 would stop the synchronous motor SM of the secondaryclock, but the closing of contacts 55-56 of the master clock cause thesecondary clock to continue to operate but at normal instead of doublespeed, through a circuit readily traced and including front contact [0|of relay R contacts 58-55 at the master clock and contacts 91-98 of thesecondary clocle.

This circuit will only be maintained closed for eleven seconds at whichtime it will be broken at contacts 55-55, and was established to reclosecontacts 95-96 of the secondary clock, so

that the high speed circuit including these contacts 95-96 as well ascontacts 54-55 of the master clock may be re-established. During theclosure of the low speed circuit including contacts 55-56 of the masterclock the shaft 50 was running double speed while the shaft 90 wasrunning at only normal speed, so that the secondary clock may have lostapproximately ten seconds. This will, however, be corrected at the endof the next hour for reasons heretofore explained. Upon reclosing ofcontacts 54-55 of the master clock contacts 95-96 of the secondary clockhaving also been reclosed the secondary clock resumes its double speed,through a circuit including these contacts. At approximately the tenminute position of the master clock the synchronous winding motor SMwill have caused the main spring H to have been fully wound and willcause the contact spring 04 to engage the pin 85 thereby opening thecontacts 84-85 and deenergize relay R gization of relay R causes thecontact 60 to drop to apply 60 cycle current to the electric synchronousmotor portion of the master clock, that is, to the synchronous motor 8Minstead of 120 cycles. This causes the shaft 50 to rotate atDeenernormal speed instead of double speed. This shaft now correctlymanifests time. Dropping of the relay R opens its contact I03 and stopsthe winding motor 5M Also dropping of the relay R removes 220 volt 120'cycle current from the secondary clock by the opening of front contactI02 and causes the application of 110 volt cycle current thereto by theclosing of back contact NH. The secondary clock will now operate atnormal speed and will indicate time correctly except that it is nowapproximately eleven seconds slow. This small error will however becorrected at the end of the hour for reasons and in a manner as alreadyexplained. Although as pointed out above the contact 54-55-56 controlledby cam K are shown to assume an ab-- normal position between the 60minute and the 60:22 minute position of the master clock these contactsmay be constructed to actually assume the abnormal position for a wholeminute after the 60 minute position. This latter construction wouldallow for greater discrepancy between the secondary and the masterclock. It would however cause the secondary clock to be about onehalfminute slow which error would be corrected at the end of the next hour.

Fig. 3 structura-The system shown in Fig. 3 employs a master clocksimilar to that illustrated in Fig. l, in that the escapement clock isone of the continuously operated type, which clock is synchronized withthe frequency of the alternating current which is regulated to correctlymanifest the passing of time. The system of Fig. 3 itself is similar tothat illustrated in Fig. 2 in that double frequency current is employedto cause a secondary clock to catch up, so to speak. The frequencydoubler including thyratron tubes TR and TR is identical to the oneshown in 2 for which reason it will not be described. This system shownin Fig. 3 is similar to those shown in Figs. 1, 2, 6 and '7, and is onewhere the secondary clocks are corrected immediately upon return ofpower after a power failure or current cessation and wherein asupplemental and more accurate correction of secondary clocks is madeperiodically, as for instance, at the end of each hour.

There is, however, one important difference between the systems of Figs.1 and 2 and Fig. 3, and that is that the system in-Fig. 3 will onlycorrect a fast secondary clock providing it is not more than one minutefast and that is accomplished by removing the low frequency current atthe end of the fifty-ninth minute and not reapplying it until the end ofthe sixtieth minute (end of hour) and by applying double frequency tothe H circuit during the last minute of the hour. This construction doesnot require a contact operated by the secondary clock in the high low orH -L circuit, and permits a correction to be made after a currentcessation wholly by the relay R which relay is picked up at thetermination of the current cessation and not dropped until after havingbeen energized for a time equal to such duration when it is dropped.This relay R by the closing of front contact HI shunts the contactsll2-I l3 controlled by the cam or disk K so that the contact H5 of relayR can apply either 60 cycle volt curto prevent both windings on thesynchronous motors of the secondary clocks S being energized at th sametime by alternating current of double frequency, because this mightcause over saturation of the synchronous motor and possibly inaccuracyin its speed of operation.

Referring to Fig. 3, like in Fig. 1 the pendulum I26 is synchronized byan electro-magnet !2I-i22 which is provided with rubber shoes, so tospeak, to dampen the noise due to the pendulum striking theelectro-magnet and also to afford something resilient for the pendulumto bounce away from. It may be pointed out that the pendulum I26 if slowis accelerated by bouncing away from the rubber and if fast is retardedby being held toward the electro-ma net during each magnetic pulse untilthe magnet is dcenergized. When the pendulum is slow it has not reachedthe rubber bumper when the magnetic impulse is terminated, but thependulum is close enough to have been accelerated by such impulse as aresult of which the fast approaching pendulum strikes the rubber bumperand then. bounces away from it. The electromagnet is preferablyenergized for a moment at the end of each pendulum swing when thewinding motor SM is operated from 60 cycle current and energized fourtimes for each pendulum cycle when the winding motor is operating doublespeed due to being energized by 120 cycle 220 volt alternating current.Like in the Fig. 1 construction intermittent energization of theelectro-magnet I2II22 is accomplished through the medium of commutator I25 driven through the medium of gear I23 and pinion I24 by thesynchronous winding motor SSM This doubling of the electro-magneticimpulses as compared with the number of engagements of the pendulum I29with the electro-magnet iZl-IZZ when the synchronous motor SM isoperating at normal speed is resorted to to effect less domination ofthe electro-magnet over the pendulum when the pendulum is out of step orsynchronism with the electro-magnetic impulses. It has been experiencedthat if only one magnetic pull per pendulum cycle is employed that thereis a tendency for the electro-magnet to stop the pendulum when themagnetic pulses and the pendulum swings ar in phase opposition. Thisdetrimental effect is entirely eliminated by the employment of doublefrequency magnetic pulses as compared with the pendulum frequency. Thereis also another difference between the master clock of Fig. 3 from thatshown in Fig. 1 and that is that the correcting cams K and K are drivendirectly by the escapement mechanism and therefore operate during theduration of current cessation. The advantage of having the correctingcams a direct part of the master escapement is that they will be alittle more accurate than cams located on the winding shaft as is truein Fig. l. The inaccuracy in the Fig. 1 construction can however be keptas low as one second and since this inaccuracy is not cumulative it maybe disregarded.

Operation Fig. 3.Under normal conditions, that is 'betwen the zeroposition and the fiftynine minute position of the master clock MC andwhen no current cessation has taken place the synchronous winding motorSM winds the escapement clock main spring I26 at exactly the rate thatthe escapement portion of the clock unwinds the main spring I26, so thatthe contacts I 28-429 remain just barely open. Under this normalcondition the secondary clock S is connected to the secondary winding ofthe 60 cycle transformer T through the following cirouit: beginning atthe upper terminal of this secondary winding, back contact I I5 of therelay R contacts II2-I I3 operated by cam K and closed only during thefirst fifty-nine minutes of the hour as manifested by the master clock,line wire fi -L winding of the synchronous motor 5M operating one of thesecondary clocks S through gear reduction I32 in a manner such thatshaft I33 and minute hand I34 rotate at 1 R. P. H. when the synchronousmotor is operating at synchronous speed with regulated 50 cycle currentapplied thereto, through the common return wire C back to the otherterminal of this secondary winding.

When the master clock reaches the fifty-nine minute position thecontacts II2I i3 operated by the cam K open and the contacts iI'I-l l8operated by the cam K close, This operation of these contacts removeslow frequency current (60 cycle) from the high-low wire H L and applieshigh frequency current cycles) to the high wire H This high frequencycircuit starts at the upper terminal of the secondary of the transformerT back contact I I6 of the relay R contacts II1I I8 operated by the camK and closed only during the sixtieth minute of the hour as manifestedby the master clock, high wire H contacts !3l] I3I controlled by the camK of the secondary clock, through the first winding of the synchronousmotor 8M through the common return wire 0 back to the transformer T Ifthe secondary clock E3 was fast to an extent less than one minute itwill be held at the sixty minute position and if it was slow less thanone minute it will be advanced during the sixtieth minute of the masterclock to the sixty minute position at which point the circuit is openedat contacts I3d-I3l by the secondary clock S At the end of the sixtiethminute of the master clock as manifested by the hand I35 and thepositions assumed by the cams K and K the contacts II'I-I I8 will openand the contacts II2-I l3 will reclose as a result of which 120 cyclecurrent will be cut off the wire H extending to secondary clocks S and60 cycle current will be reapplied to the high-low wire H L Let us nowassume that a current cessation occurs at the fifty minute position ofthe master clock M0 and the secondary clock S and that this currentcessation continues until the fifty-eight minute position is assumed bythe master clock. The master clock will continue to run in spite of thefact that the winding motor stops the main spring having at least anhour and possibly as much as twenty-four hours reserve of energy. Uponreturn of alternating current at the fifty-eight minute position of themaster clock M0 the contacts I28--i 29 being closed the relay R will beenergized. Opening of the back contact I I6 of this relay merely opensthe line circuit at a second point it already being open at contactsII1II8. The lifting of contact II5 applies double frequency alternatingcurrent to the winding motor 5M thereby causing this synchronous motorto operate at double normal speed, which will cause it to catch up afteran interval of running equal to the time of the current cessation thatis at the six minute position of the master clock. The lifting of thiscontact II5 also applies 120 cycle current to the synchronous motor SMof the secondary clocks S through the high frequency circuit includingthe high-low wire H .L This high frequency .cir

cuit may be traced as follows: starting at the upper terminal of thesecondary winding of transformer T front contact H of relay R frontcontact H l of the relay R wire H L the other winding of the synchronousmotor 5M common return wire C to the bottom terminal of said secondarywinding. During the time of correction, that is, between the fifty-eightminute and the six minute position of the master clock MC the contactsll2-Il3 and Ill-Il8 will be operated, but this will not have any affecton the secondary clocks because the circuit leading to contacts ll1--lI8 is open at back contact H6 of relay R. and the contacts I|2H3 areshunted by the front contact III of the relay R It is thus seen thatpower failure error of the secondary clocks may be corrected even thoughsuch correction extends through the even hour position of the masterclock, and also independent of cam operated contacts for which reasonthe cams K and K may be located directly on a continuously rotatingmaster clock shaft as illustrated in Fig. 3. That is, in the structureof Fig. 3 the secondary clock correction that is made immediately aftera current cessation is made wholly by the relay R controlled through themedium of re-winding contact I28l29, and is made through a circuit whichdoes not include secondary clock operated contacts. a

Fig. 6 structure.-The modification shown is a system which functions thesame as that shown in Fig. 1, but instead of showing two control linewires energized at different times by current of one character Fig. 6employs a single control line energized at different times by differentcharacter currents. It will be noted that in Fig. 1 the contacts 35, 35,3'! and 4| apply alternating current to the control lines L H whereas inFig. 6 these same contacts are connected in reverse order and applyeither pulsating current of one polarity or pulsating current of anotherpolarity to the single control line L H The secondary clock of Fig. 6 isthe same as that shown in Fig. 1 except that two rectifiers RI and RIand transformers T and T have been added. The rectifier R1 incombination with transformer T serves to convert pulsating current ofnegative polarity to alternating current and apply it to contacts 42-43from whence it may at times reach the high speed synchronous motor SMthrough wire 46; whereas the rectifier R1 in combination withtransformer T will convert pulsating current of positive polarity intoalternating current and apply it to the contacts 38--38 which contactswhen closed allow th s alternating current to reach the low speed motorSM (see Fig. 1) through wire 45.

Operation Fig. 6.The system of Fig. 6 operates the same and performs'thesame function in a different way as Fig. 1 for which reason it isbelieved unnecessary to discuss this operation. Fig. 7 structure.Thesecondary clocks of Fig. '1 are identical to the secondary clocks ofFig. 1 and the master clock of Fig. 7 is identical to that of Fig. 2except that the contacts operated by the cams K and K and the relay Rcontacts are connected in reverse order between a source of current andthe control wires, and the electric clock portion of the master clock isdriven by one or the other of two synchronous motors (not shown) as isthe rewind shaft of the master clock of Fig. 1 instead of being drivenat two different speeds by applying alternating currents of twodifferent frequencies to a single synchronous motor as indicated in Fig.2. In Fig. 2 the line wire L is switched from one source of current (60cycle) to another source of current (120 cycle) as conditions require,whereas in Fig. 7 one source of current (60 cycle) is switched from onecontrol line (L") to another control line (H as conditions require.Referring to Fig. 2 it should be noted that contacts and 58 areconnected to the control line wire L whereas in Fig. 7 these samecontacts are connected directly to the source of alternating current.Also in Fig. 2 the contact fill of relay R is connected to the lowfrequency source (60 cycle) whereas in Fig. 7 this contact I0! isconnected to the low speed wire L and that the contact 102 of relay R ofFig. 2 is connected to the high frequency source (120 cycle) whereasthis contact H12 in Fig. 7 is connected to the high speed line H". It isthus apparent that the master clock of Fig. 2 as used in Fig. '7 appliesalternating current to the low speed line wire for those time periodsthat the master clock of Fig. 2 applies low frequency alternatingcurrent to the only control line wire, and that the master clock used inFig. 7 applies alternating current to the high speed line wire duringthose time periods that the master clock of Fig. 2 applies highfrequency current to the only control line wire.

Operation of Fig. 7.-Since the system illustrated conventionally in Fig.7 performs the same functions as does the system of Fig. 2 and employsdifferent apparatus only for performing such function it is believedunnecessary to describe its operation.

Fig. 4 construction and operation.Referring to Fig. 4 the rewindorganization of each of Figs, 1, 2, 3, 6 and '7 is preferablyconstructed as illustrated in this figure. In the constructionillustrated in Fig. 4 the main gear 4 has a threaded centeropeningprovided with a left-hand thread. This gear 4 is then screwed onto theleft-hand thread 12 on the shaft l2. The construction is such that withthe main spring fully wound the wheel 4 is screwed onto this shaft [2 alongitudinal distance such that the pin I! upon further winding byrotation of shaft l2 will cause the insulated portion I5 of contactspring l5 to engage this pin II. The inner end of main spring 3 is ofcourse fastened to the shaft l2 at a point so as not to interfere withthe threaded engagement between shaft l2 and gear 4. By thisconstruction a current cessation of as much as five hours may becorrected, because rotation of the pin I1 about the shaft 92 in aclockwise direction is freely permitted for a plurality of revolutions.

' After cessation of current has ceased the rewind motor will operatethe shaft in a clockwise direction for the same number of revolutions,that is, until the insulated portion l5 of the contact l5 again engagesthe pin I'l.

Fig. 5 construction and operation.In Fig. 5 has been illustrated how acontinuously operated one revolution per minute shaft of any one of thesecondary clocks of Figs. 1, 2, 3, 6 and '7 may be converted into anintermittently operated one revolution per hour shaft. Such anintermittently driven hour shaft (1 R. P. H.) is desirable where thesecondary clock is employed to record or register time in suitableintervals preferably minute intervals. In the construction illustratedit is proposed to register minute intervals by the type wheel 23%. Inthe construction shown the shaft 231 is operated by the synchronousmotors of one of the secondary clocks shown in Figs. 1, 2, 3, 6 or '7 ina clockwise direction and at a speed of one revolution per minute. Thearm 232 pivoted at 233 and having a lug 232 has its lug engage the cam234 keyed or otherwise fastened to the shaft 23!. This arm 232 haspivoted thereto a pawl 235 so shaped that it will engage the teeth ofthe ratchet wheel 236 and when it has operated this ratchet wheel 236 anare equal to one ratchet tooth this pawl will bind under the pin 23?, soas to avoid overthrow. That is, to avoid the ratchet wheel 236 beingturned more than one tooth one-sixtieth of a revolution for eachrotation of the shaft 23L The arm' 232 is biased to the right by aspring 238 and the pawl 235 is biased down by the spring 239. Theholding pawl 240 is pivoted to a stationary support by a pivot 2M and isurged in engagement with the ratchet Wheel 2336 by a spring 242. Fromthe construction illustrated in Fig. 5 it is readily seen that duringthe major part of each revolution of the shaft 23! the arm 232 isgradually moved toward the left and that at the end of each minute, orother suitable interval, the lug 232 slips off of the cam 234 therebycausing the ratchet wheel 236 to be advanced in a clockwise directionsix degrees, or an amount equal to one minute. This wheel 236 operatesthe type wheel 236, and for each operation of the pawl 235 advances thistype wheel to the next minute number. This type wheel may throughsuitable means operate other type wheels intermittently, once for eachtype character thereon, to indicate the hour of the day, the day of theweek or month, and the like.

Summary The systems of secondary clock operation and correctionillustrated in Figs. 1, 2, 3, 6 and 7 show how secondary clocks of verysimple and economic construction may be corrected in accordance with amaster clock and how this master clock may be controlled in accordancewith. cycle passage of an alternating current derived from a commercialpower system which has its frequency regulated to correctly manifest thepassing of time. Not only does each of these systems correct thesecondary clocks after each current cessation but supplementalcorrections are made after equal time intervals thereafter by apparatusfunctioning in a manner so that if errors occur these errors are notcumulative. To clarify this statement, if a correction is made byspeeding up a secondary clock in accordance with the duration of acurrent cessation each of a plurality of such errors that such apparatusmight make would be added together. If on the other hand a secondaryclock is speeded up until it reaches a particular time indication asdetermined by stop means within the secondary clock any error that suchapparatus might make would be reflected in the same way as the severalhands of aclock are sometimes not in agreement, i. e. these errors wouldbe present but would not be reoccurring additively.

It should be understood that even though in the system shown in Figs. 2and 3 the high frequency current is double in frequency of that of thelow frequency current that any other ratio of frequencies may be usedwithin limits. Also that the speed ratios between high speed and lowspeed synchronous motors of the systems shown in Figs. 1, 6 and 7 mayvary from that of three to one illustrated. Also, the cam shafts mayhave a normal speed of two or more revolutions per hour instead of 1 R.P. M. as illustrated. Also. referring to the systems shown in Figs. 1

and 3 instead of employing an electro-magnet only On one side of thependulum, two electromagnets one on each side of the pendulum may beemployed, in which case both electro-magnets are preferably energizedeither once or twice for each pendulum cycle. Referring to Fig, 3 thecams K and K may be mounted on the winding shaft containing contactsl28-|29, it of course being understood that these two shafts normallyoperate at the same speed. Such a construction has already beenillustrated in Fig. 1. The 3600 R. P. M. synchronous motors 8M SM, SM SMSM", SM and 6M are preferably of the construction shown in Warren PatentNo. 1,546,- 269, whereas the 1200 R. P. M. synchronous motors SM and 8Mare preferably of the construction shown in the Toewe Patent No.1,788,813.

It is desired to point out that, if desired, the contacts 38--39 of thesecondary clocks of Figs. 1, 6 and 7 and the contacts 9'I-98 of thesecondary clocks of Fig. 2 maybe omitted. These contacts have beenprovided to correct a secondary clock that is more than one minute fast.If a secondary clock is fast less than one minute it may be correctedbecause of the fact that the normal current is removed from thesecondary clock during the sixtieth minute of the hour and thesecontacts contribute nothing insofar as correcting a secondary clock thatis fast less than one minute and these contacts have been provided tocorrect a clock which is fast to a greater extent. If these contacts38-39 or-Sl-BB are omitted it is possible to correct by the end-ofhourcorrecting means, shown in each of Figs, 1, 2, 6 and 7, a clock that isslow as much as fiftynine minutes. This is done by imposing a pluralityof corrections, one during each hour, of about two minutes each for thesystems shown in Figs. 1, 6 and '7 and of about one minute each for thesystem shown in Fig. 2.

Also, if desired, the Fig. 2 and Fig. 7 constructions may be modified byincluding a contact controlled by the cam K and open between the timeindicating positions of 60:00 and 60:22 in the energizing circuit ofrelay R This would cause the usual correction to take place in the sameway at the end of hour position of the secondary clocks even duringthose times when the contacts 84-85 are closed which manifests that theshaft 50 is still tardy, and at the same time it would cause the extentof rewind to stay in step with the extent of corrections made upon thesecondary clocks. In this case the contacts 54, 55 and 56 may beomitted.

Fig. 8 structure-Also, if desired, as shown in Fig. 8 of the drawings,an auxiliary source of alternating current, such as a standbyalternating current generator, of either the rotary or the vibratorytype, may be used to keep the secondary clocks operating approximatelyin accordance with the lapse of time during a cessation of thealternating current of regulated frequency. This auxiliary source ofalternating current need not generate current of the precise frequencybut should do so within possibly one half of one percent. In accordancewith this modification a power-off relay PO is employed which isenergized directly from the source of alternating current of regulatedfrequency, so that if this source of alternating current fails the relayPO will assume its retracted position. Dropping of the relay PO willresult in the generation of alternating current. In the construction ofFig. 8 this is done by closure of the direct current circuit includingthe battery 240, the back contact 2 of the relay PO, and the interruptercontact 243 of the interrupter IN. This will cause pulsating directcurrent of approximately sixty cycles to flow in the primary winding 244of the interrupter IN, resulting in the generation of alternatingcurrent of approximately 60 cycles in the secondary winding 245 of thisinterrupter IN, the interrupter armature being a tuned reed tuned tothis frequency. Also, with the power-off relay in its retractedcondition this auxiliary source of alternating current is through theback contact 246 of this relay PO applied directly to the double-throwcontact 249 controlled by the master clock cam K directly connected tothe shaft 241 of any suitable master clock. This master clock is,however, preferably one of the type dominated by the source ofalternating current of regulated frequency when such current isavailable such as shown in Figs. 1, 2 and 3 of this application and inmy prior applications above referred to. The master clock is,

v however, not dominated by the auxiliary source of alternating currentbecause the un-dominated master clock has better time keeping qualitiesthan does the auxiliary source of alternating current.

Operation Fig. 8.-Referring to Fig. 8, normal- 1y when alternatingcurrent of regulated frequency is present and during the firstfifty-nine minutes of the hour this alternating current flows to the lowspeed motor of the secondary clock S", which is exactly the same as thatshown in Fig. 1. During the last minute of the hour the contacts shift,thereby applying current to the high speed synchronous motor (shown inFig. 1) of the secondary clock S and causes the secondary clock S to beadvanced until it reaches the zero minute position when the conacts42-43 of the secondary clock S open. When the master clock reaches thisend-of-hour position the alternating current of regulated frequency isreapplied to the low speed wire L so that thereafter the secondary clockwill run in exact synchronism with the alternating current dominatedmaster clock. During alternating current cessation the secondary clock Sis corrected in exactly the same manner as just explained. If a currentcessation occurs the auxiliary source of alternating current will besubstituted for the source of regulated frequency as long as thecessation continues, and there will be some error in the time indicationof the secondary clock until it is corrected at the end of the hour. Inthose cases where alternating current of regulated frequency is notavailable at any time the master clock will not be so dominated in theFig. 8 construction, in which case the endof-hour corrections will beentirely relied upon to correct the secondary clocks in accordance withthe master clock. In the Fig. 8 construction if a power failure existswhile the master clock passes through the last minute of the hour theauxiliary source of alternating current will be used for correcting thesecondary clocks. It is thus seen that the secondary clocks in the Fig.8 system are kept in continuous operation except for a short time duringcorrecting periods and that a clock that is less than two minutes slowor one that is less thanone minute fast will be corrected.

Also, if desired the wires 45 and 46 may be connected together andconnected directly to the low speed synchronous motor 8M of Fig. l, thehigh speed synchronous motor SM being omitted,

but in this latter construction the gear ratio of the secondary clock issuch that the shaft 3| (Fig. 1) makes one complete revolution during theflow of 213,000 cycles of current instead of during 216,000 cycles ofcurrent. Also the clock dial (see Fig. 9) will be'constructed so thatthe minute indicating hand indicates time correctly, that is, advancesto the next minute number on the dial for each 3600 cycles of current.It thus becomes apparent that the space between the 59th minute and the60th minute on the dial (see Fig. 9) will span an arc that is onlyonesixth as large as the arc spanned by each of the first fifty-nineminutes. It thus becomes apparent that if alternating current ofregulated frequency is available the secondary clock will be held backfifty seconds during the last minute of each hour by the opening andreclosing of contact 3839 and 42--43 of the secondary clock. It is, ofcourse, also understood that if the secondary clock should be fast toany extent up to fifty-nine minutes it will be corrected for reasonspointed out in connection with Fig. 1 and that if the secondary clock isslow to an extent of fifty seconds or less it will be corrected by beingstopped forless than fifty seconds. other words, in this modifiedconstruction the sixtieth minute on the clock dial spans only an arc often seconds of time and the clock if slow is stopped for less than fiftyseconds at the end of the hour and is stopped the full fifty secondperiod at the end of the hour if it was correct when the fifty nineminute ten second position was reached. Inthis modified construction theauxiliary source of current IN (Fig. 8) should be correct within onepercent so that a current cessation for a period of one hour will notproduce an error of more than fifty seconds so that this error may becorrected at the end of such hour. Obviously since the secondary clockis corrected at the end of each hour a current cessation of any numberof hours could not get the secondary clocks out of synchronism with eachother or the master clock. A clock dial for thismodified secondary clockconstruction has been shown in Fig. 9.

It is of course understood that each of the synchronous motors disclosedin this application is self starting. The self-starting feature of thesesynchronous motor is due to the fact that their rotors, which in eachcase constitutes a thin disk of permanent magnet steel, have sufficientresidual magnetism to result in hysteresis torque when a magnetic fieldpasses through the plane of the disk. This residual magnetism alsoleaves permanent magnetic poles and results in synchronous operationwhen the disk is brought near to synchronous speed. Also, it should beunderstood that instead of having the corrections made hourly by havingsuitable cams on shafts rotated l R. P. H. these cams may he on shaftsrotated one revolution in two hours or in any other desired time period.

Having thus shown and described several. embodiments of clock systemsexemplifying my invention it is desired to'be understood that theparticular arrangements, speed ratios, frequency ratios and the likehave been selected to facil tate description of the invention and havenot been illustrated as illustrations of the specific constructionspreferably employed in practicing the invention. It should therefore beunderstood that various modifications and adaptations may be made tofacilitate application of the invention to the problems encountered inpracticing the invention without departing from the spirit of theinvention except as demanded by the scope of the appended claims.

What I claim as new is:

1. In a clock system including a master clock and a secondary clock; thecombination with a master clock which indicates standard time, asecondary clock normally indicating substantially the same time asindicated by said master clock including a high speed shaft and aself-starting synchronous motor means having a rotor mounted directly onsaid shaft, line wires connecting said master clock and said secondaryclock, means including contact mechanism controlled by said master clockfor applying operating alternating current to said line wires and tosaid secondary clock to cause said secondary clock to operate atsubstantially the same speed as said master clock so long as nocessation of alternating current occurs and to cause said high speedshaft to operate at increased speed for a time proportional to the timeduration of such cessation after such cessation and to thereafter applyoperating current to said line wires and said secondary clock to againoperate said secondary clock at the speed of said master clock to causesaid secondary clock to indicate sub stantially correct time after atemporary current cessation has occurred, and means including said meansand also including other contact mechanism controlled by said masterclock and including contact mechanism associated with said secondaryclock efiective between predetermined chronological conditions of saidmaster clock and said secondary clock to correct said secondary clockperiodically during times of no current cessation.

2. In a clock system; the combination with a source of alternatingcurrent; a master clock comprising a first means for measuring thepassing of time and a second means for measuring the duration of acessation of alternating current from said source; a secondary clockincluding a time shaft and a self-starting alternating current snchronous motor including a rotor for driving said shaft; line wiresconnecting said master clock and said secondary clock; means includingsaid line wires and said second means for during the supply ofalternating current operating said rotor at normal speed from saidsource and for causing said rotor to operate from current derived fromsaid source at higher speed after each cessation of said alternatingcurrent for a time period equal to the normal speed divided by thedifference between the higher speed and the normal speed and multipliedby the duration of such cessation; and other means including said linewires and said first means and also including contacts operated by saidsecondary clock for bringing said secondary clock into chronologicalsynchronism with said master clock periodically during times of nocurrent cessation.

3. In combination a master clock shaft rotated to substantiallycorrectly manifest the passing of time and to indicate standard time, asource of alternating current, a secondary clock including a high speedshaft having a low speed and a high speed rotor mounted thereon, saidsecondary clock also including a low speed stator associated with saidlow speed rotor and a high speed stator associated with said high speedrotor,

line circuit means connecting said master clock and said secondaryclock, means including contacts operated by said master clock shaft tocontrol said line circuit means to cause said low speed stator to beenergized during a first time interval of a time period and to causesaid high speed stator to be energized during a second time interval ofsaid time period, means controlled by said secondary clock when itreaches a predetermined chronological condition to prevent furtheroperation of said secondary clock' by said high speed stator, and meansincluding other contacts operated by said master clock shaft forcontrolling said line circuit means after each cessation of saidalternating current for energizing said high speed stator for a timeinversely proportional to the difference of the speeds of said rotorwhen driven by their respective stators divided by the speed of the lowspeed rotor when driven by its stator and directly proportional to theduration of said current cessation.

4. In combination a master clock shaft rotated to substantiallycorrectly manifest the passing of time and to indicate standard time, asource of alternating current, a secondary clock including a high speedshaft having a low speed and a high speed rotor mounted thereon, a lowspeed stator associated with said low speed rotor and a high speedstator associated with said high speed rotor, line circuit meansconnecting said master clock and said secondary clock, means includingcontacts operated by said master clock shaft to control said linecircuit means to cause said low speed stator to be energized during afirst time interval of a time period and to cause said high speed statorto be energized during a second time interval of said time period, andmeans controlled by said secondary clock when it reaches a predeterminedchronological condition to prevent further operation of said secondaryclock by said high speed stator, whereby said secondary clock startsfrom said predetermined chronological condition at the beginning of eachtime period.

5. In a clock system, a first source of alternating current, a secondsource of alternating current, a master clock shaft, reduction gearing,a self-starting synchronous motor, a secondary clock having a time shaftconnected directly and permanently through said reduction gearing tosaid self-starting synchronous motor, line wires extending from saidmaster clock to said secondary clock,.means controlled by said masterclock for normally supplying said self-Starting synchronous motor withalternating current from said first source over said line wires, meanseffective in response to a current cessation from said first source forconnecting said secondary source to said synchronous motor over saidline wires for a time to operate said synchronous motor substantiallythe same number of additiqnal revolutions that it would have operatedhad no current cessation taken place, and other means including contactson said master clock and contacts on said secondary clock effectivebetween predetermined chronological conditions of said master clock andsaid secondary clock to correct said secondary clock, said other meansfunctioning periodically during times of no current cessation.

6. In a clock system, the combination with two self-starting synchronousmotors, two sources of alternating current of regulated frequency onesource being of high frequency and the other source being of lowfrequency with said frequencies sufficiently close to each other so thatboth are capable of operating said self-starting synchronous motors butat different speeds, an escape mechanism including an oscillatorymember, a main spring for driving said escape mechanism, anelectro-magnet for holding said oscillatory member at rest, a rectifier,a direct current for energizing said electro-magnet derived by therectification of alternating current from one of said sources by saidrectifier so that said electro-magnet is deenergized upon cessation ofcurrent from said one source, rewinding means for rewinding said mainspring driven by one of said synchronous motors energized only when saidmain spring is partly unwound providing there is no current cessation, atime shaft normally indicating standard time driven by the other of saidsynchronous motors which other synchronous motor is energized byalternating current of said low frequency source when said main springis fully wound and there is no cessation of current from said one sourceand energized by current of said high frequency when said main spring ispartly unwound and there is no cessation of current from said onesource, and a bucking coil on said electro-magnet having a resistance torender said oscillatory member slow releasing to the same extent thatthe other of said synchronous motors will gain as compared with thenumber of cycles applied thereto when such synchronous motor istemporarily deenergized followed by high frequency energization thereofimmediately after a temporary current cessation, whereby said escapemechanism will accurately measure the time lost by said time shaftduring a current cessation and whereby said time shaft indicatesstandard time when said main spring is fully wound, and a secondaryclock controlled by said time shaft.

'7. In a primary-secondary clock system, the combination with a sourceof alternating current of regulated frequency regulated to correctlymanifest the passing of time, a master clock including escapementmechanism for substantially correctly manifesting the passing of timeduring cessation of said alternating current and for indicating standardtime and including alternating current controlled means to manifest thepassing of time correctly as determined by the alternating current cyclepassage of said source during the supply of alternating current fromsaid source, a secondary clock including a selfstarting synchronousmotor means having a rotor, line wires connecting said master clock andsaid secondary clock, means including contact mechanism operated by saidmaster clock for controlling the application of alternating current oversaid line wires to said secondary clock to cause said secondary clock tooperate in perfect synchronism with said master clock during thepresence of said alternating current of regulated frequency andeffective after each cessation of alternating current to cause saidrotor to operate at increased speed for a time period proportional tosaid cessation and at a rate so that said secondary clock will indicateatfer such period substantially the same time that it would haveindicated had no current cessation occurred, and means including saidmeans and also including additional contact mechanism operated by saidmaster clock and contacts operated by said secondary clock toperiodically correct said secondary clock with respect to said masterclock during times when no current cessation occurs.

8. In a two-unit master clock, the combination with two self-startingsynchronous motors, two sources of alternating current one source beingof high frequency and the other source being of low frequency with saidfrequencies sufficiently close to each other so that both are capable ofoperating said self-starting synchronous motors but at different speeds,an escape mechanism including an oscillatory member, a main spring fordriving said escape mechanism, an electromagnet for holding saidoscillatory member at rest, a rectifier, a direct current for energizingsaid electro-magnet derived by the rectification of alternating currentby said rectifier from one of said sources so that said electro-magnetis deenergized upon cessation of current from said one source, rewindingmeans for rewinding said main spring driven by one of said synchronousmotors energized only when said main spring is partly unwound providingthere is no current cessation, a time shaft normally indicating standardtime driven by the other of said synchronous motors which othersynchronous motor is energized by alternating current of said lowfrequency source when said main spring is fully wound and there is nocessation of current from said one source and energized by current ofsaid high frequency when said main spring is partly unwound and there isno cessation of current from said one source, and a bucking coil on saidelectro-magnet having a resistance to render said oscillatory memberslow releasing to the same extent that the other of said synchronousmotors will gain as compared with the number of cycles applied theretowhen such synchronous motor is temporarily deenergized followed by highfrequency energization thereof immediately after a temporary currentcessation, whereby said escape mechanism will accurately measure thetime lost by said time shaft during a current cessation and whereby saidtime shaft indicates standard time when said main spring is fully wound,a secondary clock including a time shaft and a third synchronous motorfor driving said secondary clock time shaft, a line circuit connectingsaid master clock and said secondary clock, two pairs of contactsoperated by said time shaft of said secondary clock one pair opened fora short are of movement of said time shaft at the end of each revolutionthereof and the other pair opened for a short are of movement of saidtime shaft just before the end of each revolution thereof, a filterallowing only the free flow of high frequency alternating currentconnected in series with said one pair of contacts, a filter allowingonly the free flow of low frequency alternating current connected inseries with said other pair of con tacts, said serially connectedcontacts and filters being connected in multiple with each other andthen in series with said third synchronous motor and said line circuit,and contacts controlled by the time shaft of said master clock forapplying alternating current of low frequency during a first portion ofa revolution of each time shaft of said master clock and for applyingalternating current of high frequency during the remaining portion ofsuch revolution of said time shaft of said master clock to said linecircuit.

9. In a synchronous motor clock system, the combination with a secondaryclock including a time shaft, synchronous motor means for driving saidtime shaft including a high speed circuit branch and a low speedcircuitbranch for operating said time shaft at high speed or a low speedrespectively depending upon whether said high speed circuit branch orsaid low speed circuit branch is energized, a pair of contacts includedin series in said high speed circuit branch controlled by said timeshaft and opened when said time shaft reaches the end of a time periodposition and remaining open for a short are of movement of said timeshaft, and a master clock effective to energize said high speed circuitbranch with alternating current during the last portion of such timeperiod as manifested by said master clock and for energizing said lowspeed circuit branch with alternating current during the remainingearlier portion of such time period.

10. In an alternating current clock system, a a

source of alternating current, a master clock including two units one ofwhich substantially accurately reflects the passing of time and theother of which in combination with the first unit measures the durationof a cessation of alternating current from said source, a secondaryclock having a time shaft, two synchronous motors having differentsynchronous speeds when energized by alternating current from saidsource having their rotors secured to said shaft, contacts controlled bysaid time shaft open for a short interval at the end of each time periodas refiected by said secondary clock included in series with thesynchronous motor having a high speed, a transformer for each of saidsynchronous motors, a filter for one transformer allowing only pulsatingcurrent of one polarity to flow through it included in series with theprimary winding of one of said transformers, a filter allowing onlypulsating current of the opposite polarity to flow through it includedin series with the primary winding of the other of said transformers, acircuit including the secondary winding of one of said transformers andsaid low speed synchronous motor in series, another circuit includingthe secondary winding of the other of said transformers said high speedsynchronous motor and its associated contacts in series, a line circuit,and means controlled by said master clock for transmitting over saidline circuit and to the filters of said secondary clock pulsatingcurrent of one polarity after each current cessation and during thelatter portion of said time period as reflected by said master clock andfor transmitting over said line circuit and to the filters of saidsecondary-clock pulsating current of the opposite polarity during theremaining portion of such period.

11. In a synchronous motor clock system, the combination with asecondary clock including a time shaft, two synchronous motors eachcapable of directl driving said time shaft which motors if energizedseparately by currents of the same frequency will operate said timeshaft at different speeds, a source of pulsating current of onepolarity, a source of pulsating current of the opposite polarity, bothsaid sources of pulsating current being of the same frequency, a pair ofcontacts included in series with the synchronous motor which drives saidtime shaft at the higher speed, a line circuit, a rectifier for allowingpulsating current of one polarity to fiow included in an energizingcircuit for energizing said motor driving said time shaft at the higherspeed, a rectifier for allowing pulsating current of the oppositepolarity to flow included in an energizing circuit for the other of saidsynchronous motors, and a master clock for applying pulsating current ofsaid one polarity through the medium of said line circuit to saidrectifiers during the last portion of a time period and for applyingpulsating current of the opposite polarity to said rectifiers throughthe medium of said line circuit during the remaining earlier portion ofsaid time period.

12. In a synchronous motor clock system,

the V combination with a secondary clock including a time shaft, twosynchronous motors each capable of directl driving said time shaft whichmotors if energized separately by currents of the same frequency willoperate said time shaft at different speeds, a source of alternatingcurrent, a pair of contacts controlled by said time shaftv and includedin series with one of said synchronous motors which motor if energizedby said alternating current drives said time shaft at the higher speed,two transmitting circuits one including said pair of contacts and thesaid one synchronous motor and the other transmitting circuit includingthe other synchronous motor, and a master clock for applying periodiccurrent from said source to said one transmitting circuit during thelast portion of a time period for correcting said secondary clock andfor applying periodic current from said source to the other of saidtransmitting circuits during the remaining earlier portion of such timeperiod for advancing said secondary clock in accordance with the lapseof time, whereby a fast clock is retarded because said other circuit isclosed during less than said period of time and a slow clock is advancedby said one synchronous motor when included in said one circuit.

13. In a synchronous motor clock system, the combination with asecondary clock having a high speed circuit branch and a low speedcircuit branch, a time shaft included in said secondary clock, a geartrain for driving said time shaft, synchronous motor means directly andcontinuously operatively connected to drive said time shaft through themedium of said gear train, said synchronous motor means being common toboth of said circuit branches and operating said time shaft at a highspeed when said high speed circuit branch is energized by alternatingcurrent and operating said time shaft at a low speed when said low speedcircuit branch is energized by alternating current, a pair of contactsin said high speed circuit branch controlled by said time shaft andopened when said time shaft assumes H the zero time position and for ashort are of movement of said time shaft beyond such zero time position,a source of alternating current, and means including a master clockhaving a master time shaft and associated contact mechanisms forenergizing said high speed circuit branch during the latter portion of arevolution of said master time shaft and. also after termination of acessation of alternating current from said source for a timeproportional to the duration of such cessation and for applyingenergizing current to said low speed circuit branch when said high speedcircuit branch is not energized,

14. A time indicating system comprising in combination, a master clock,a secondary clock including a synchronous motor and time manifestingmeans driven by said synchronous motor, means including contactscontrolled by said master clock and a circuit leading from said masterclock to said secondary clock to at times supply fluctuating currentofone character to said secondary clock over said circuit to operate saidsecondary clock through the medium of its synchronous motor at a normalspeed and to at other times supply fluctuating current distinctive incharacter from said current of one character tooperate said secondaryclock through the medium of its synchronous motor at a higher thannormal speed, and means controlled by said secondary clock to at timesblock the flow of one of said currents and to at other times block theflow of the other of said currents.

15. A time indicating system according to the preceding claim whereinthe characters of currents comprise two currents of differentfrequencies.

16. A time indicating system according to claim 14 wherein thecharacters of currents comprise pulsating currents of the same frequencybut of different polarities.

17. A time indicating system comprising in combination, time manifestingmeans, a' gear train for driving said time manifesting means, a twospeed rotary synchronous motor means including two circuits and fordriving said gear train, said motor means being constructed and arrangedto operate at one synchronous speed when alternating current from aregulated frequency source is applied to one of said circuits and tooperate at a higher synchronous speed when current from the same sourceof alternating current is applied to the other circuit thereof each ofsaid synchronous speeds bearing a constant ratio to the frequency ofsaid alternating current, a master clock, and means controlled by saidmaster clock and said gear train to at times energize one circuit ofsaid synchronous motor means and to at other times energize said anothercircuit of said synchronous motor means by alternating current from saidregulated frequency source.

18. A time indicating system comprising in combination, time manifestingmeans, a shaft for driving said time manifesting means, a two speedrotary synchronous motor means including a first circuit branch and asecond circuit branch, said motor means being constructed and arrangedto operate at one synchronous speed when alternating current from aregulated frequency source is applied to said first circuit branch andoperate at a higher synchronous speed when current from the same sourceof alternating current is applied to said second circuit branch each ofsaid synchronous speeds bearing a constant ratio to the frequency ofsaid alternating current, a master clock, and means controlled by saidmaster clock and said shaft to at times energize said first circuitbranch of said synchronous motor means and to at other times energizesaid second circuit branch of said synchronous motor means byalternating current from said regulated frequency source.

19. In combination, a master clock including a time shaft which by itsrotation substantially correctly manifests the passing of time, a sourceof alternating current having its frequency regulated to manifestaccurately by cycle passage the passing of time and available at saidmaster clock, a secondary clock including time manifesting means and asynchronous motor for driving said means at a speed to indicate thepassing of time in accordance with the cycle passage of the alternatingcurrent applied thereto and also including correcting means foroperating its time manifesting means at a higher speed when energized byalternating current of the same frequency, a circuit extending from saidmaster clock to said secondary clock controlled by contacts operated bysaid time shaft for supplying alternating current from said frequencyregulated source of alternating current to said synchronous motor, asecond circuit extending from said master clock to said secondary clockand connected to said correcting means to at times operate said timemanifesting means at said higher speed, and means controlled by the timeshaft of said master clock for at times applying alternating currentfrom said frequency regulated source to said second circuit.

20. In an alternating current clock system, the combination with asource of alternating current having its frequency regulated tocorrectly manifest the passing of time, a master clock including a firstmeans for measuring the lapse of time in accordance with the number ofcycles of alternating current received and a second means for measuringthe duration of a cessation of such alternating current, a secondaryclock including a synchronous motor means normally energized byalternating current from said source to drive said secondary clock at anormal rate, advancing means including said synchronous motor means fordriving said secondary clock at an excessive rate, and correcting meansfor periodically correcting said secondary clock by rendering saidadvancing means active which corrects said secondary clock in acordanewith time periods measured by said first means when no current cessationoccurs and corrects said secondary clock in accordance with time periodsmeasured by said second means when a current cessation has taken placesince said secondary clock was last corrected.

21. In combination; a master clock; a secondary clock including timemanifesting means and a synchronous motor for driving the same; a sourceof alternating current of regulated frequency supplying current to apoint adjacent said master clock; a line circuit connecting said clocks;means including said line circuit and including contacts controlled bysaid master clock for normally supplying current from said source tosaid secondary clock to cause it to manifest correctly the passing oftime so long as said contacts are closed and no cessation of alternatingcurrent occurs and for supplying current to said secondary clock tocause it to operate at a higher than normal rate after each alterhatingcurrent cessation for a time proportional to said cessation to correctsaid secondary clock, and other means including said line circuit andother contacts controlled by said master clock for periodicallysupplying current to correct said secondary clock irrespective of acurrent cessation.

' OSCAR I-I.DICKE.

